As I wrote earlier, referring to a WSJ piece, 'Humans, Lions Struggle to Co-Exist', Aug. 8-9, p. A7:

"Africa's human population is the fastest growing in the world. In roughly the same period as the lion decline (42 percent over 21 years), the number of Africans has doubled to nearly 1.2 billion people. The population will double again to 2.5 billion by 2050 according to the United Nations."

Adding:

More people "has meant more forests being turned into pastures, more locals hunting lions' prey for their own meals - leading to starving lions- and more herders killing lions rather than risking cattle."

The process noted above is all too clear: exploding human numbers, especially in Africa and Asia, are not only contributing to human mass migration but also the leveling of forests and decimation of many species. In fact, a new study out of Stanford University by geoscientist Jonathan Payne points to a new mass extinction event (the 6th) of which we are right in the middle. Arguably, most people - including environmentalists- aren't even aware it.

The Stanford -based study published in Science looked at 2,497 different marine animal groups at one taxonomic level above the level of species called genera. They found that increases in an organism's body size were linked to an increased risk of extinction in the present period. More puzzling, they found this was not the case in the Earth's distant past.

What was missing then, but is present now - to drive the current extinction? Here's a prime clue: During the preceding 66 million years there was actually a not insignificant link between smaller body sizes and going extinct. In other words, the mass extinction of the current period is totally reversed from that.

According to Payne, hinting at the solution:

"Human hunting has been extensive for many thousands of years on land, whereas it's been extensive for a couple of hundred years in the oceans."

Conclusion: Humans already drove to extinction many land-based, large animal species (in the Late Quaternary Extinction Event) and are now driving other large animals - mainly in the oceans - to extinction Interestingly, however, for the oceans the threats of extinction are not apportioned equally among all marine species. Instead, the largest ones - in terms of mass and body size- are the ones most threatened. Why?

Well, because these species: shark, tuna, whales ...afford the most profit in terms of human consumption or just predation (hunting -fishing). As the authors of the recent Science paper put it: "From sharks to whales, giant clams, sea turtles and tuna, the disproportionate threat to large marine organisms reflected the unique human propensity to cull the largest members of a population."

No mystery then that many ecological researchers and other biologists (e.g. John Phillips of Barbados) predict that by the middle of this century the main form of marine life will be ....wait for it...Jellyfish! This will be a result of all the remaining desirable marine species being extracted and consumed, in combination with enhanced ocean warming.

The extinction and displacement of land animals is already well under away, thanks to selective human hunting (including for sport) as well as the pernicious destruction of diverse ecosystems where humans build homes, set up farms, extend cities and erect massive wind power turbines or solar collectors. Moreover, as climate change worsens the biodiversity will crash even further, since too many species will compete for an ever decreasing resource 'pie', as well as desirable territory..

The above findings call into question the arguments by Cally Carswell in a recent article ('People and the Planet') appearing in Sierra magazine (Sept., p. 26). In it, Carswell argues against blaming increased human population for global warming - a claim which I vehemently took issue with, e.g.

"While it's true in the long term fewer people will likely result in fewer carbon emissions ...the extent to which each new person contributes to the emissions problem varies dramatically according to where and how well they live."

This is true. The reality is that the bio-productive output in different nations is not equal, and using a map of the world, Richard Attenborough (in a 2014 BBC documentary), showed the divergences, with the UK consuming 5.5 hectares per person, and the USA, 9.5 hectares. Thus, the average USA person is consuming more than four times that which is defined as a fair, equal apportioning of resources across all the numbers on the planet. According to Attenborough's expert, by this reckoning of such unequal apportioning of output, the planet can only hold 1.5 billion people. This is the upper limit of carrying capacity given the finite resources the planet actually provides.

By contrast, the hectare average is about 0.5 for each Rwandan. But it is precisely this limited bio-productive output per person that drives the ravaging of extended surrounding resources including hunting game, and destroying existing forests for charcoal burning - for fuel. Carswell extends this to conditions in Niger, writing:

"At current rates it would take a personfrom Niger about 200 years to produce the carbon the average U.S. resident produces in one year."

Which is true, but she omits a critical aspect: That Niger person may not have a Chevy Grand Cherokee belching out 6 tons of CO2 a year but he or she is raiding forests (e.g. for wood to render charcoal for fuel) and thereby decimating the primary carbon "sink". All totaled, between 1990 and 2005 Niger lost 34.9% of its forest cover or around 679,000 hectares. Meanwhile, the total rate of habitat conversion for the same interval amounted to 25. 7 percent. The habitat loss means larger mammals, reptiles could be affected, and the forest reduction means not only animal habitat destroyed but also a key CO2 absorption sink..

Carswell's argument is that population control is better achieved via greater access to higher education for women, in all nations. There is no argument with this position, but it can't be embraced while also reducing efforts to limit human numbers. Also, I take issue with the contention, from a UC- Riverside prof (Jade Sasser), she quotes to the effect that:

"To support justice for women means supporting their right to have children"

Well, only up to a point! Up to replacement level say two kids per family- yes. Beyond that, no. While I do not advocate draconian solutions such as have been applied in India (mass sterilization) and China (firm 1-child policy) there is room for removing any tax credit support - certainly in this high carbon nation. This is for anyone having more than 2 kids. They can have those extra kids, then, but receive no tax credits for them.

Time is growing short to stave off a sixth great mass extinction, but those like Carswell and Sasser seem not to grasp that means looking beyond the carbon deposition factor. It also means examining how we are adversely affecting thousands of vulnerable species that share this planet with us.

About Me

Specialized in space physics and solar physics, developed first astronomy curriculum for Caribbean secondary schools, has written thirteen books - the most recent:Fundamentals of Solar Physics. Also: Modern Physics: Notes, Problems and Solutions;:'Beyond Atheism, Beyond God', Astronomy & Astrophysics: Notes, Problems and Solutions', 'Physics Notes for Advanced Level&#39, Mathematical Excursions in Brane Space, Selected Analyses in Solar Flare Plasma Dynamics; and 'A History of Caribbean Secondary School Astronomy'. It details the background to my development and implementation of the first ever astronomy curriculum for secondary schools in the Caribbean.